A general problem in the art is to provide a procedure capable of transmitting in a secure manner audiovisual and multimedia data of high visual quality and in whatever numerical format, live or prerecorded, to a television screen, video projector or for being recorded on a hard disk or a completely different back-up device belonging to a box that connects the remote transmission network to a display of a type of monitor, television screen, video projector, or projection screen, all while preserving the audiovisual quality, but avoiding fraudulent utilization such as the possibility of making pirated copies, analog or numerical, of the films or audiovisual programs visualized via the aforementioned decoder box.
The demand for interactive multimedia services is more and more important. The distribution systems of multimedia information on DVDs or on the telecommunication network, for example, video on demand systems are in full expansion and characterized by their complexity and their insecurity with respect to pirating in spite of numerous existing procedures and systems. These distribution systems are often very expensive to implement by the user, lack security, flexible usage, and the adaptability to different clients and their needs. Moreover, they are often pirated by mal-intentioned persons in spite of the various protection or traceability procedures, such as “watermarking.” “Watermarking,” also called digital watermarking, is a technique that joins the visual or audio content, the digital content such as images, the video or audio streams. The technique consists of processing the contents to insert information in the contents. In general, the inserted information is invisible at the time of seeing the content, but can be retrieved by applying the processing of the aforementioned content. Two types of watermarks exist:
the fragile watermark: The inserted information is affected by a modification of the content; this type of watermark is used to detect if the contents have been modified;
the robust watermark: The inserted information is itself conserved even if the content is modified; this type of watermark is, for example, used to associate the royalties of an author with a work.
Certain holders of films or audiovisual programs make fraudulent copies which they then distribute via various supports (Internet, DVDs pirates). Indeed, the majority of current protection systems rely solely on protection through encrypting a digital stream. However, once decoded on the client station, the film is no longer protected and can be copied on other supports such as a simple VHS cassette, for example, with a video tape recorder connected between the video output of the decoder and the television set.
Different watermarking solutions exist that withstand the various manipulations that the aforementioned fraudulent copy can undergo to correct this problem. However, it does not permit the immediate identification of the person at the origin of the copy and, thus, the fraudulent broadcast. Copying and distribution of the pirated audiovisual programs continues without an immediate and simple visual identification of the coordinates of the persons at the origin of the fraud.
With existing solutions, it is possible to transmit films and audiovisual programs in digital form via broadcasting networks of type wireless, cable, satellite, etc., or via the telecommunication networks of type DSL or (Digital Subscriber Line) or LLR. (Local Loop Radio) or via DAB (Digital Audio Broadcasting), etc., networks. In addition, to avoid the pirating of works broadcasted in this way, the latter are often encrypted or scrambled through various well known means.
However, a main inconvenience of current solutions is that in the case of pirating of the protection system, particularly by systems of falsified chip cards or by the simulation of the encryption keys, the audiovisual works are susceptible to being broadcasted in an uncontrolled way in a perfect digital form, that is, in every respect in conformity with the original. Moreover, a single pirated copy of such an audiovisual program can enable the pirate, who is at the origin, to commercialize on a large scale the pirated work because it is perfect.
One solution consists of digitally marking the distributed digital copies. For example, US 2002/129253 discloses a procedure for processing a compressed MPEG stream that consists of directly marking the compressed MPEG signal by the modification of the values present in the stream according to a watermarking motif. However, that type of procedure does not guarantee that the mal-intentioned user could not create a copy of the protected film in another form that is different from the form in which it was supplied. In particular, those procedures do not guarantee the impossibility of producing copies of the films in the form of VHS cassettes that allow commercialization of the illicit copies. In the same way, they do not prevent production of copies of film in compressed numerical forms of the DivX or VCD type, which are one of the principal supports of pirated films available on the Internet.
WO 97/46012 discloses marking audiovisual streams based on small spatial distortions of the pixels of the video images according to selected deformation motifs. That type of marking is invisible to the eye and permits the transmission of information in the video stream without the knowledge of the person that uses it. The information permits identification of the source and date of an unauthorized copy of the video image. That type of modification is also envisaged to resist a change of support of the video, in particular, with a support on a VHS cassette, or change of format in DivX or VCD.
U.S. Pat. No. 4,528,588 discloses transmission of an encoded audiovisual signal, for example, by systems of known keys, wherein the aforementioned signal is decoded on the destination equipment and at the same time marked by identification information specific to the client equipment or its possessor. The aforementioned information is being introduced in such a way, spatially and frequentially, that its extraction is made difficult. The aforementioned information moreover being more obligatorily inserted in the stream thanks to a system implying a magnetic or chip card which contains at the same time the numerical keys necessary to decoding of the aforementioned signal and information of identification to be inserted.
The call for the decoding keys cannot be done without using identification information. The mark inserted in the stream is a binary word inserted with a system of modifications of the levels of the video signal at certain quite precise places, known to a specific device that is in charge of locating the aforementioned mark in a video stream. The mark is more invisible to complicate the task of a mal-intentioned individual who wishes to extract it. Any copy of a film thus protected, in whatever form it may be, contains the same mark as the copy of the signal from which it resulted. Thus, if a copy of a signal is identified as pirated, one can identify the person and the equipment at the origin of the fraudulent copy and, thus, condemn it. The correspondence between a mark and the individual holder of the copy is realized thanks to a data base, contained on a server contacted at the time of the renting of the video.
However, these solutions all have in common that they require the comparison between the copy of origin of a film and the copy pirated to be able to identify the mark inserted in the signal. This implies a centralization of the tests of identification in a place where the original, or the distribution of a great number of copies of the original, would be stored. In those cases, that poses practical problems and the identification of the source of a copy can, thus, become laborious.
Moreover, those solutions necessitate specific hardware and, as a consequence, specialists to carry out the identification. Indeed, many efforts are made to make the inserted mark as discrete as possible to prevent pirates from locating it and, thus, extracting it. However, the more difficult it is for a pirate to locate the mark, the more it requires complex hardware on the verification side. This is because the pirate would otherwise be able to constitute his own apparatus and thus counter the protection system. In such cases, this poses practical problems and makes identification of the source of a pirated copy laborious to obtain.
Lastly, those solutions hardly dissuade pirates from proceeding to make copies. Indeed, the inserted marks being invisible, pirates believe that they can succeed by handling the original video via changes in supports or operations. The pirate is all the more inclined to do it because the pirate knows that very few pirated copies will be tested and identified because the associated methods of identification are very difficult. Thus, even if the mark resists such manipulation, the pirate risks almost nothing in any case. With the current limitations of the current systems, many individuals do not hesitate to pirate and distribute fraudulent film copies.
It would therefore be advantageous to provide a protected system to dissuade pirates from making fraudulent copies and especially dissuade pirates from dispersing pirated works to other people.